Gripping device for cylindrical objects



1964 J. P. PILGER GRIPPING DEVICE FOR CYLINDRICAL OBJECTS Filed Oct. 31, 1961 INVQ'NTOR. James J?Pz {yer m WM United States Patent 0 3,118,698 GRIPPENG HJEVICE FOR CYLINDPJCAL GBJEUTS Ewes P. Pilg-er, Riehland, Wash, assignor to the United S-tates of America as represented by the United States Atomic Energy Commission Filed Oct. 3 1, 1951, fier. No. 149,130 1 Claim. (til. 294-102) The invention relates to a novel gripping device for cylindrical objects, more particularly to a device with positively controlled gripping jaws to insure a circumferentially uniform and stress-free grip on rods or tubes, for drawing or straightening the same.

It is essential, for certain purposes, that small thinwalled tubes be drawn to accurate sizes and straightened to within extremely small limits of error. To meet these requirements the tubes are drawn through dies or straightened by stretching, and for both these operations a gripping device is needed.

Gripping devices which are now available have been found to be unsatisfactory for aluminum, zirconium, and certain other thin-walled tubes; when the devices grip sufiiciently to carry out the drawing or stretching operations mentioned, they almost invariably deform the gripped end portion of the tube, so that this portion has to be discarded as waste. Even chucks with multiple gripping jaws create small indentations that make the end portion of the tube or rod gripped unsuitable for certain uses.

It is, accordingly, an object of the invention to provide a gripping device capable of pulling thin-walled tubes for drawing or straightening them without deforming the end portions being gripped.

It is another object to provide a gripping device for pulling thin-walled tubes or rods for drawing and straightening them, without excessively indenting the portions being gripped.

Other objects will appear as the description of the invention proceeds.

In the drawings:

FIG. 1 is a longitudinal sectional view of the device;

FIG. 2 is a transverse sectional view taken on the line 22 of FIG. 1;

FIG. 3 is a fragmentary longitudinal sectional view taken on the line 33 of FIG. 2; and

FIG. 4 is a view of the device, partly in section, taken on the line 44 of FIG. 1.

The device of the invention includes a shell it having an internal frustoconical surface 11, and an annular member 12 threa ed into one end of shell 10. Concentric with annular member 12 is annular endpiece 13, which is joined to member 12 by a plurality of capscrews 14. As shown in FIGURES 1 and 4, endpiece 13 is welded to two attaching means 15, having bolt holes 16 whereby the device may be attached to a support which is not shown.

Referring to FIGURES 1 and 3, annular member 12 has integral with it a plurality of extensions 17. Viewed from the side as in these views, they resemble a segment of a trapezoid which has been out along its altitude, with one sloping edge 17a, and a vertical edge 17b. The sloping edge 17a is in close contact with the inner surface 11 of shell 16 along its len th, held there in a fixed posi tion by the threaded connection between shell 1t and member 12. The vertical edge 37b is in close but slidable contact with slotted sleeve 18.

As shown in FIGURE 2, the cross-sectional shape of extensions 17 is that of a shouldered keystone varying in size from large to small when considered in a direction away from the annular member 12, as is evident from a comparison of the right-hand half of FIG. 2 with the left-hand half. The extensions 17 and the inner frustoconical surface 1 of the shell 10 define a plurality of T-slots 19 of the same size, the vertical bar or leg of each T-slot decreasing in length when considered in a direction leading away from the annular member 12, and the cross bar of each T-siot remaining constant in width and thickness.

The extensions 17 are suitably curved on their sloping edges 17a and vertical edges 17b in order to fit the inner frustoconical surface 11 of the shell lb and the outer cylindrical surface of the sleeve 18, respectively.

Into one end of sleeve 18 is threaded a plate 20. Plate 29 is attached by screw 21 to U-shaped bracket 22, which, in turn, is attached by means of Wrist pin 23 to arm 24. it is to be understood that arm 24 leads to some impelling menas (not shown) for moving sleeve 18 lengthwise within extensions 17 of annular member 12.

As can be seen in FIGURES 1, 2 and 3, sleeve 18 has a plurality of longitudinal slots 25 through which an equal plurality of jaw members 26 project when the sleeve is in a forward position as shown in FIGURE 1, and in the left side of FIGURE 2. As shown in FIGURE 1, jaw members 26 when viewed from the side are in the shape of a trapezoid which has been cut along its altitude like extensions 17, but their altitude is less than that of extensions 17, being equal to the length of slots 25. Their sloping sides 26a are in close but slidable contact with the inside surface 11 of shell 14 and their straight sides 2612 are furnished with teeth for gripping a cylindrical shape 28, which may be a tube or rod to be drawn, stretched, or pulled.

As shown in FIGURE 2 jaw members 26 are T-shaped in cross section, with the heads or cross bars of the T being along the sloping sides 26a and being received in the heads or cross bars of the T-slots 19. The legs of the T-shaped jaw members lie in the legs of the T-slots l9 and project therefrom through the slots 25 in the sleeve 1% to the interior thereof.

1 aw members 26 fit snugly within the slots 2.5 of sleeve 18, and since the plurality of curved surfaces 17b of extensions 17 also hold sleeve 18 snugly, jaw members 26 are positively prevented from rolling longitudinally, or parallel with the axis of sleeve 18.

When sleeve 18 is moved lengthwise of the extensions 17, the jaw members 26 also move lengthwise of the extensions 17, since the jaw members fit the slots 25 in the sleeve 18. As the jaw members 26 move lengthwise as stated, they move radially toward or away from the cylindrical shape 28 to be gripped by the jaw members. This is due to the engagement of the sloping sides 26a of the jaw members with the frustoconical inner surface 11 of the shell 18.

Pull may now be applied to the rear through arms 15 to draw object, or shape 28 through a die, or to stretchstraighten it, as the case may be, or for any other operation of a similar nature. Or, as will be understood, arms 15 may be bolted to a fixed member (not shown), and the pull exerted from the other end of shape 28, this is not being material so far as the present invention is concerned.

It will be understood that this invention is not to be limited to the details given herein, but that it may be modified within the scope of the appended claim.

What is claimed is:

A multiple jaw gripping device for cylindrical shapes, comprising an outer shell with inner frustoconical walls, an annular back member attached to the shell and having a plurality of extensions in close contact with the inner side of the shell, the said extensions being approximately shouldered keystone shaped in cross section and defining a first plurality of T-shaped slots parallel with the shell and an inner right cylindrical space coaxial with the shell and extending through a major portion of its length, an inner sleeve within the right cylindrical space snugly slidable Within the extensions and having a second plurality of slots equal to the first plurality, a like plurality of gripping jaws of approximately T-shape in cross section, the arms of which T-shapes being slidably held against the inner Wall of the shell by the shoulders of the keystone shapes of said extensions and the bases of which pass through the both pluralities of slots, the length of said jaws parallel to the axis of the sleeve being about equal to the length of the slots in the sleeve, and means for advancing and retracting said sleeve coaxially with the shell Within said right cylindrical space, whereby the jaws may be placed in a fixed, radial position, thereby gripping a cylindrical object circumferentially With a controlled, uniform radial pressure.

References Cited in the file of this patent UNITED STATES PATENTS 

